The American physicist Peter J. Lu discovered that the ancient Chinese not only knew about diamonds, but also used them in the jewellery industry. Chinese artists used diamond gravel to polish and cut jade, sapphire and other precious stones. Many precious stones have a hardness almost comparable to diamonds – the fine abrasion of the diamond dust is ideally suited to working them.

So how did the scientist Peter J. Lu arrive at this amazing discovery? At Harvard Graduate School of Arts and Sciences he conducted research on four ceremonial axes, each decorated with a large sapphire, these the first relics in which sapphires were used. Three axes were made 4000-3800 BC, the fourth in 3500 BC, and the first three relics were to be found in the final resting places of the aristocracy of the Sanxingcun and Liangzhu cultures; the largest is 22 cm, the smallest 13 cm. Initially, the physicist suspected that the sapphires ornamenting the axes were polished quartz, yet quartz sand does not produce such ideal results. Quartz is simply less hard than diamond, while sapphire, as a variety of corundum, is harder too. Peter J. Lu conducted many analyses of the sapphires on the axes – including with the aid of an electron microscope – and found that the surface of the stone is polished to the level of contemporary standards. For the polishing of corundum at present it is precisely diamond which is used! Interestingly, quite close by the site at which the axes were found is a diamond deposit. Peter J. Lu thinks that the relics he studied are evidence for the use of diamonds by the jewellers of ancient China and thus the earliest example of their use in the history of the world.